. >>> serious firefighting in los angeles, california. they're still trying to figure out what started this massive fire overnight. it housed a cleaning business and print company. thick black smoke backed up traffic on the busy 101 freeway for hours. it took 125 firefighters nearly two hours to knock that fire down. nobody was injured. >>> tonight the heroic work of firefighters is coming to life in a new nbc drama, "chicago fire," focusing on the emotional toll of the high-risk job. it aims to get in the intense mind-set of those facing trauma and danger every day. "chicago fire" airs at 10:00 right here on nbc. >>> the real firefighters here in the district are constantly adapting to change. they have the tough task of keeping up with 1,000 new residents every month. jackie bensen has a look behind the scenes to the brave men and women that goes way beyond fighting fires. >> reporter: d.c. fire and ems captain mark meacham is responding to a 911 call at an acosta senior high school. students are complaining of stomach pains. before 9/1